Nikolas Haass

RAB27A promotes melanoma cell invasion and metastasis via regulation of pro‐invasive exosomes

Publisher: Wiley

Date: 03-01-2019

DOI: 10.1002/IJC.32064

Abstract: Despite recent advances in targeted and immune-based therapies, advanced stage melanoma remains a clinical challenge with a poor prognosis. Understanding the genes and cellular processes that drive progression and metastasis is critical for identifying new therapeutic strategies. Here, we found that the GTPase RAB27A was overexpressed in a subset of melanomas, which correlated with poor patient survival. Loss of RAB27A expression in melanoma cell lines inhibited 3D spheroid invasion and cell motility in vitro, and spontaneous metastasis in vivo. The reduced invasion phenotype was rescued by RAB27A-replete exosomes, but not RAB27A-knockdown exosomes, indicating that RAB27A is responsible for the generation of pro-invasive exosomes. Furthermore, while RAB27A loss did not alter the number of exosomes secreted, it did change exosome size and altered the composition and abundance of exosomal proteins, some of which are known to regulate cancer cell movement. Our data suggest that RAB27A promotes the biogenesis of a distinct pro-invasive exosome population. These findings support RAB27A as a key cancer regulator, as well as a potential prognostic marker and therapeutic target in melanoma.

In vivo overexpression of Emi1 promotes chromosome instability and tumorigenesis

Publisher: Springer Science and Business Media LLC

Date: 11-04-2016

DOI: 10.1038/ONC.2016.94

Abstract: Cell cycle genes are often aberrantly expressed in cancer, but how their misexpression drives tumorigenesis mostly remains unclear. From S phase to early mitosis, EMI1 (also known as FBXO5) inhibits the anaphase-promoting complex/cyclosome, which controls cell cycle progression through the sequential degradation of various substrates. By analyzing 7403 human tumor s les, we find that EMI1 overexpression is widespread in solid tumors but not in blood cancers. In solid cancers, EMI1 overexpression is a strong prognostic marker for poor patient outcome. To investigate causality, we generated a transgenic mouse model in which we overexpressed Emi1. Emi1-overexpressing animals develop a wide variety of solid tumors, in particular adenomas and carcinomas with inflammation and lymphocyte infiltration, but not blood cancers. These tumors are significantly larger and more penetrant, abundant, proliferative and metastatic than control tumors. In addition, they are highly aneuploid with tumor cells frequently being in early mitosis and showing mitotic abnormalities, including lagging and incorrectly segregating chromosomes. We further demonstrate in vitro that even though EMI1 overexpression may cause mitotic arrest and cell death, it also promotes chromosome instability (CIN) following delayed chromosome alignment and anaphase onset. In human solid tumors, EMI1 is co-expressed with many markers for CIN and EMI1 overexpression is a stronger marker for CIN than most well-established ones. The fact that Emi1 overexpression promotes CIN and the formation of solid cancers in vivo indicates that Emi1 overexpression actively drives solid tumorigenesis. These novel mechanistic insights have important clinical implications.

Growth and adaptation mechanisms of tumour spheroids with time-dependent oxygen availability

Publisher: Cold Spring Harbor Laboratory

Date: 24-04-2022

DOI: 10.1101/2022.04.24.489294

Abstract: Tumours are subject to external environmental variability. However, in vitro tumour spheroid experiments, used to understand cancer progression and develop cancer therapies, have been routinely performed for the past fifty years in constant external environments. Furthermore, spheroids are typically grown in ambient atmospheric oxygen (normoxia), whereas most in vivo tumours exist in hypoxic environments. Therefore, there are clear discrepancies between in vitro and in vivo conditions. We explore these discrepancies by combining tools from experimental biology, mathematical modelling, and statistical uncertainty quantification. Focusing on oxygen variability to develop our framework, we reveal key biological mechanisms governing tumour spheroid growth. Growing spheroids in time-dependent conditions, we identify and quantify novel biological adaptation mechanisms, including unexpected necrotic core removal, and transient reversal of the tumour spheroid growth phases.

Detection of Primary Melanoma in Individuals at Extreme High Risk A Prospective 5-Year Follow-up Study

Publisher: American Medical Association (AMA)

Date: 08-2014

DOI: 10.1001/JAMADERMATOL.2014.514

Abstract: The clinical phenotype and certain predisposing genetic mutations that confer increased melanoma risk are established however, no consensus exists regarding optimal screening for such in iduals. Early identification remains the most important intervention in reducing melanoma mortality. To evaluate the impact of full-body examinations every 6 months supported by dermoscopy and total-body photography (TBP) on all patients and sequential digital dermoscopy imaging (SDDI), when indicated, on detecting primary melanoma in an extreme-risk population. Prospective observational study from February 2006 to February 2011, with patients recruited from Sydney Melanoma Diagnostic Centre and Melanoma Institute Australia who had a history of invasive melanoma and dysplastic nevus syndrome, history of invasive melanoma and at least 3 first-degree or second-degree relatives with prior melanoma, history of at least 2 primary invasive melanomas, or a CDKN2A or CDK4 gene mutation. Six-month full-body examination compared with TBP. For equivocal lesions, SDDI short term (approximately 3 months) or long term (≥6 months), following established criteria, was performed. Atypical lesions were excised. New primary melanoma numbers, characteristics, and cumulative incidence in each patient subgroup effect of diagnostic aids on new melanoma identification. In 311 patients with a median (interquartile range [IQR]) follow-up of 3.5 (2.4-4.2) years, 75 primary melanomas were detected, 14 at baseline visit. Median (IQR) Breslow thickness of postbaseline incident melanomas was in situ (in situ to 0.60 mm). Thirty-eight percent were detected using TBP and 39% with SDDI. Five melanomas were greater than 1 mm Breslow thickness, 3 of which were histologically desmoplastic the other 2 had nodular components. The benign to malignant excision ratio was 1.6:1 for all lesions excised and 4.4:1 for melanocytic lesions. Cumulative risk of developing a novel primary melanoma was 12.7% by year 2, with new primary melanoma incidence during the final 3 years of follow-up half of that observed during the first 2 years (incidence density ratio, 0.43 [95% CI, 0.25-0.74] P = .002). Monitoring patients at extreme risk with TBP and SDDI assisted with early diagnosis of primary melanoma. Hypervigilance for difficult-to-detect thick melanoma subtypes is crucial.

Real‐time cell cycle imaging during melanoma growth, invasion, and drug response

Publisher: Wiley

Date: 27-06-2014

DOI: 10.1111/PCMR.12274

Abstract: Solid cancers are composed of heterogeneous zones containing proliferating and quiescent cells. Despite considerable insight into the molecular mechanisms underlying aberrant cell cycle progression, there is limited understanding of the relationship between the cell cycle on the one side, and melanoma cell motility, invasion, and drug sensitivity on the other side. Utilizing the fluorescent ubiquitination-based cell cycle indicator (FUCCI) to longitudinally monitor proliferation and migration of melanoma cells in 3D culture and in vivo, we found that invading melanoma cells cycle actively, while G1-arrested cells showed decreased invasion. Melanoma cells in a hypoxic environment or treated with mitogen-activated protein kinase pathway inhibitors remained G1-arrested for extended periods of time, with proliferation and invasion resuming after re-exposure to a more favorable environment. We challenge the idea that the invasive and proliferative capacity of melanoma cells are mutually exclusive and further demonstrate that a reversibly G1-arrested subpopulation survives in the presence of targeted therapies.

Reciprocal Regulation of BRN2 and NOTCH1/2 Signaling Synergistically Drives Melanoma Cell Migration and Invasion

Publisher: Elsevier BV

Date: 07-2022

DOI: 10.1016/J.JID.2020.12.039

Abstract: Phenotypic plasticity drives cancer progression, impacts treatment response, and is a major driver of therapeutic resistance. In melanoma, a regulatory axis between the MITF and BRN2 transcription factors has been reported to promote tumor heterogeneity by mediating switching between proliferative and invasive phenotypes, respectively. Despite strong evidence that subpopulations of cells that exhibit a BRN2

Cell Cycle Checkpoint and DNA Damage Response Defects as Anticancer Targets: From Molecular Mechanisms to Therapeutic Opportunities

Publisher: Springer Netherlands

Date: 14-10-2014

DOI: 10.1007/978-94-017-9421-3_3

A Novel Class of Anticancer Compounds Targets the Actin Cytoskeleton in Tumor Cells

Publisher: American Association for Cancer Research (AACR)

Date: 13-08-2013

DOI: 10.1158/0008-5472.CAN-12-4501

Abstract: The actin cytoskeleton is a potentially vulnerable property of cancer cells, yet chemotherapeutic targeting attempts have been h ered by unacceptable toxicity. In this study, we have shown that it is possible to disrupt specific actin filament populations by targeting isoforms of tropomyosin, a core component of actin filaments, that are selectively upregulated in cancers. A novel class of anti-tropomyosin compounds has been developed that preferentially disrupts the actin cytoskeleton of tumor cells, impairing both tumor cell motility and viability. Our lead compound, TR100, is effective in vitro and in vivo in reducing tumor cell growth in neuroblastoma and melanoma models. Importantly, TR100 shows no adverse impact on cardiac structure and function, which is the major side effect of current anti-actin drugs. This proof-of-principle study shows that it is possible to target specific actin filament populations fundamental to tumor cell viability based on their tropomyosin isoform composition. This improvement in specificity provides a pathway to the development of a novel class of anti-actin compounds for the potential treatment of a wide variety of cancers. Cancer Res 73(16) 5169–82. ©2013 AACR.

Genome-wide gain-of-function screen for genes that induce epithelial-to-mesenchymal transition in breast cancer.

Publisher: Impact Journals, LLC

Date: 16-08-2016

DOI: 10.18632/ONCOTARGET.11314

HDAC inhibitors restore BRAF‐inhibitor sensitivity by altering PI3K and survival signalling in a subset of melanoma

Publisher: Wiley

Date: 20-12-2017

DOI: 10.1002/IJC.31199

Abstract: Mutations in BRAF activate oncogenic MAPK signalling in almost half of cutaneous melanomas. Inhibitors of BRAF (BRAFi) and its target MEK are widely used to treat melanoma patients with BRAF mutations but unfortunately acquired resistance occurs in the majority of patients. Resistance results from mutations or non-genomic changes that either reactivate MAPK signalling or activate other pathways that provide alternate survival and growth signalling. Here, we show the histone deacetylase inhibitor (HDACi) panobinostat overcomes BRAFi resistance in melanoma, but this is dependent on the resistant cells showing a partial response to BRAFi treatment. Using patient- and in vivo-derived melanoma cell lines with acquired BRAFi resistance, we show that combined treatment with the BRAFi encorafenib and HDACi panobinostat in 2D and 3D culture systems synergistically induced caspase-dependent apoptotic cell death. Key changes induced by HDAC inhibition included decreased PI3K pathway activity associated with a reduction in the protein level of a number of receptor tyrosine kinases, and cell line dependent upregulation of pro-apoptotic BIM or NOXA together with reduced expression of anti-apoptotic proteins. Independent of these changes, panobinostat reduced c-Myc and pre-treatment of cells with siRNA against c-Myc reduced BRAFi/HDACi drug-induced cell death. These results suggest that a combination of HDAC and MAPK inhibitors may play a role in treatment of melanoma where the resistance mechanisms are due to activation of MAPK-independent pathways.

Friends or foes: IL‐10 and TGF‐β in melanoma

Publisher: Wiley

Date: 27-03-2015

DOI: 10.1111/EXD.12661

BCL-XL and MCL-1 are the key BCL-2 family proteins in melanoma cell survival

Publisher: Springer Science and Business Media LLC

Date: 24-04-2019

DOI: 10.1038/S41419-019-1568-3

Abstract: Malignant melanoma is one of the most difficult cancers to treat due to its resistance to chemotherapy. Despite recent successes with BRAF inhibitors and immune checkpoint inhibitors, many patients do not respond or become resistant to these drugs. Hence, alternative treatments are still required. Due to the importance of the BCL-2-regulated apoptosis pathway in cancer development and drug resistance, it is of interest to establish which proteins are most important for melanoma cell survival, though the outcomes of previous studies have been conflicting. To conclusively address this question, we tested a panel of established and early passage patient-derived cell lines against several BH3-mimetic drugs designed to target in idual or subsets of pro-survival BCL-2 proteins, alone and in combination, in both 2D and 3D cell cultures. None of the drugs demonstrated significant activity as single agents, though combinations targeting MCL-1 plus BCL-XL, and to a lesser extent BCL-2, showed considerable synergistic killing activity that was elicited via both BAX and BAK. Genetic deletion of BFL-1 in cell lines that express it at relatively high levels only had minor impact on BH3-mimetic drug sensitivity, suggesting it is not a critical pro-survival protein in melanoma. Combinations of MCL-1 inhibitors with BRAF inhibitors also caused only minimal additional melanoma cell killing over each drug alone, whilst combinations with the proteasome inhibitor bortezomib was more effective in multiple cell lines. Our data show for the first time that therapies targeting specific combinations of BCL-2 pro-survival proteins, namely MCL-1 plus BCL-XL and MCL-1 plus BCL-2, could have significant benefit for the treatment of melanoma.

Formation and growth of co-culture tumour spheroids: new compartment-based mathematical models and experiments

Publisher: Cold Spring Harbor Laboratory

Date: 22-12-2022

DOI: 10.1101/2022.12.21.521515

Abstract: Co-culture tumour spheroid experiments are routinely performed to investigate cancer progression and test anti-cancer therapies. Therefore, methods to characterise and interpret coculture spheroid growth are of great interest. However, co-culture spheroid growth is complex. Multiple biological processes occur on overlapping timescales and different cell types within the spheroid may have different characteristics, for ex le proliferation rate or response to nutrient availability. There is no standard, widely-accepted mathematical model of such complex spatio-temporal growth processes. Typical approaches to analyse these experiments focus on the late-time temporal evolution of spheroid size and overlook early-time spheroid formation, spheroid structure and geometry. Here we make theoretical and practical contributions. We develop a general framework, based on mathematical and statistical modelling, to analyse a series of co-culture experiments. Using a range of different mathematical models we provide new biological insights about spheroid formation, growth, and structure. In addition, we extend a general class of compartment-based monoculture spheroid mathematical models to describe multiple populations and provide mechanistic biological insight. The framework is well-suited to analyse spheroids grown with multiple different cell types and the new class of mathematical models provide opportunities for further mathematical and biological insights.

Abrogation of RAB27A expression transiently affects melanoma cell proliferation

Publisher: Wiley

Date: 26-06-2020

DOI: 10.1111/PCMR.12903

PTEN: A novel target for vitamin D in melanoma

Publisher: Elsevier BV

Date: 04-2022

DOI: 10.1016/J.JSBMB.2022.106059

Abstract: Melanoma is the most dangerous form of skin cancer, with poor prognosis in advanced stages. Vitamin D, also produced by ultraviolet radiation, is known for its anti-proliferative properties in some cancers including melanoma. While vitamin D deficiency has been associated with advanced melanoma stage and higher levels of vitamin D have been associated with better outcomes, the role for vitamin D in melanoma remains unclear. Vitamin D synthesis is initiated upon UVB exposure of skin cells and results in formation of the active metabolite 1,25-dihydroxyvitamin D3 (1,25D). We have previously demonstrated that 1,25D plays a role in protection against ultraviolet radiation-induced DNA damage, immune suppression, and skin carcinogenesis. In this study 1,25D significantly reduced cell viability and increased caspase levels in human melanoma cell lines. This effect was not present in cells that lacked both phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a well-known tumour suppressor, and the vitamin D receptor (VDR). PTEN is frequently lost or mutated in melanoma. Incubation of selected melanoma cell lines with 1,25D resulted in significant increases in PTEN levels and downregulation of the AKT pathway and its downstream effectors. This suggests that 1,25D may act to reduce melanoma cell viability by targeting PTEN.

Abrogation of RAB27A expression transiently affects melanoma cell proliferation

Publisher: Cold Spring Harbor Laboratory

Date: 27-12-2219

DOI: 10.1101/2019.12.27.889329

Abstract: The role of the small GTPase RAB27A as an essential melanosome trafficking regulator in melanocytes is well-accepted. A decade ago, RAB27A was identified as a tumor dependency gene that promotes melanoma cell proliferation. RAB27A has since been linked to another propeller of cancer progression: exosome secretion. We have recently demonstrated that RAB27A is overexpressed in a subset of melanomas. High RAB27A gene and protein expression correlates with poor prognosis in melanoma patients. Mechanistic investigations revealed that the generation of pro-invasive exosomes was RAB27A-dependent and, therefore, silencing RAB27A reduced melanoma cell invasion in vitro and in vivo . However, previous studies have implicated RAB27A to be involved in both proliferation and invasion of melanoma cells. In this study, we demonstrate that the effects of abrogating RAB27A expression on proliferation are temporary, in contrast to the previously reported persistent effects on tumor invasion and metastasis. Therefore, we assist in the dissection of the short-term versus long-term effects of RAB27A knockdown on melanoma cell proliferation, invasion, and metastasis. We believe that our findings provide novel insights into the effects of RAB27A blockade. RAB27A is known to serve as an essential regulator for melanosome trafficking. However, to date its role in melanoma biology has not been completely deciphered. While there are consistent independent reports on the pro-invasive effects of RAB27A, there are conflicting data on its impact on cell proliferation. Here we show that indeed abrogation of RAB27A does reduce cellular proliferation however, this effect is only transient, while the impact on invasion as reported previously is persistent. This finding offers an explanation for the apparent contradiction in the literature and provides a deeper understanding of RAB27A function in melanoma cell biology.

microRNA-7-5p inhibits melanoma cell proliferation and metastasis by suppressing RelA/NF-?B

Publisher: Impact Journals, LLC

Date: 17-05-2016

DOI: 10.18632/ONCOTARGET.9421

The MC1R r allele does not increase melanoma risk in MITF E318K carriers

Publisher: Oxford University Press (OUP)

Date: 05-03-2023

DOI: 10.1093/BJD/LJAD041

Abstract: Population-wide screening for melanoma is not cost-effective, but genetic characterization could facilitate risk stratification and targeted screening. Common Melanocortin-1 receptor (MC1R) red hair colour (RHC) variants and Microphthalmia-associated transcription factor (MITF) E318K separately confer moderate melanoma susceptibility, but their interactive effects are relatively unexplored. To evaluate whether MC1R genotypes differentially affect melanoma risk in MITF E318K+ vs. E318K– in iduals. Melanoma status (affected or unaffected) and genotype data (MC1R and MITF E318K) were collated from research cohorts (five Australian and two European). In addition, RHC genotypes from E318K+ in iduals with and without melanoma were extracted from databases (The Cancer Genome Atlas and Medical Genome Research Bank, respectively). χ2 and logistic regression were used to evaluate RHC allele and genotype frequencies within E318K+/– cohorts depending on melanoma status. Replication analysis was conducted on 200 000 general-population exomes (UK Biobank). The cohort comprised 1165 MITF E318K– and 322 E318K+ in iduals. In E318K– cases MC1R R and r alleles increased melanoma risk relative to wild type (wt), P & 0.001 for both. Similarly, each MC1R RHC genotype (R/R, R/r, R/wt, r/r and r/wt) increased melanoma risk relative to wt/wt (P & 0.001 for all). In E318K+ cases, R alleles increased melanoma risk relative to the wt allele [odds ratio (OR) 2.04 (95% confidence interval 1.67–2.49) P = 0.01], while the r allele risk was comparable with the wt allele [OR 0.78 (0.54–1.14) vs. 1.00, respectively]. E318K+ cases with the r/r genotype had a lower but not significant melanoma risk relative to wt/wt [OR 0.52 (0.20–1.38)]. Within the E318K+ cohort, R genotypes (R/R, R/r and R/wt) conferred a significantly higher risk compared with non-R genotypes (r/r, r/wt and wt/wt) (P & 0.001). UK Biobank data supported our findings that r did not increase melanoma risk in E318K+ in iduals. RHC alleles/genotypes modify melanoma risk differently in MITF E318K– and E318K+ in iduals. Specifically, although all RHC alleles increase risk relative to wt in E318K– in iduals, only MC1R R increases melanoma risk in E318K+ in iduals. Importantly, in the E318K+ cohort the MC1R r allele risk is comparable with wt. These findings could inform counselling and management for MITF E318K+ in iduals.

NFIB Mediates BRN2 Driven Melanoma Cell Migration and Invasion Through Regulation of EZH2 and MITF

Publisher: Elsevier BV

Date: 02-2017

DOI: 10.1016/J.EBIOM.2017.01.013

Phenotypic melanoma heterogeneity is regulated through cell-matrix interaction-dependent changes in tumor microarchitecture

Publisher: Cold Spring Harbor Laboratory

Date: 11-06-2020

DOI: 10.1101/2020.06.09.141747

Abstract: Phenotypic heterogeneity of cancer cells plays a critical role in shaping treatment response. This type of heterogeneity is organized spatially with specific phenotypes, such as sharply demarcated clusters of proliferating and cell cycle-arrested cells, predominating within discrete domains within a tumor. What determines the occurrence of specific tumor cell phenotypes in distinct microdomains of solid cancers is poorly understood. Here, we show that in melanoma spatial organization of phenotypic heterogeneity is dictated by the expression and activity of MITF. We reveal that this lineage survival oncogene controls ECM composition and organization, and ROCK-driven mechanotransduction through focal adhesion maturation and actin cytoskeleton functionality. In turn, altered tumor microarchitecture and structural integrity impact tumor solid stress which then mediates phenotypic heterogeneity through p27 Kip1 . Rho-ROCK-myosin signaling is necessary to transmit the effect of the reciprocal cell-ECM regulation into phenotypic heterogeneity. Our findings place cell-ECM crosstalk as a central driver of phenotypic tumor heterogeneity. Phenotypic heterogeneity is a major culprit of cancer therapy failure. We demonstrate that phenotypic heterogeneity is controlled through tumor cell-ECM crosstalk resulting in altered tumor microarchitecture, mechanotransduction and Rho-ROCK-myosin signaling. Melanoma shares these physical properties with any solid cancer underscoring the importance of our findings for therapeutically targeting this phenomenon.

Acetylsalicylic Acid Governs the Effect of Sorafenib in RAS-Mutant Cancers

Publisher: American Association for Cancer Research (AACR)

Date: 28-02-2018

DOI: 10.1158/1078-0432.CCR-16-2118

Abstract: Purpose: Identify and characterize novel combinations of sorafenib with anti-inflammatory painkillers to target difficult-to-treat RAS-mutant cancer. Experimental Design: The cytotoxicity of acetylsalicylic acid (aspirin) in combination with the multikinase inhibitor sorafenib (Nexavar) was assessed in RAS-mutant cell lines in vitro. The underlying mechanism for the increased cytotoxicity was investigated using selective inhibitors and shRNA-mediated gene knockdown. In vitro results were confirmed in RAS-mutant xenograft mouse models in vivo. Results: The addition of aspirin but not isobutylphenylpropanoic acid (ibruprofen) or celecoxib (Celebrex) significantly increased the in vitro cytotoxicity of sorafenib. Mechanistically, combined exposure resulted in increased BRAF/CRAF dimerization and the simultaneous hyperactivation of the AMPK and ERK pathways. Combining sorafenib with other AMPK activators, such as metformin or A769662, was not sufficient to decrease cell viability due to sole activation of the AMPK pathway. The cytotoxicity of sorafenib and aspirin was blocked by inhibition of the AMPK or ERK pathways through shRNA or via pharmacologic inhibitors of RAF (LY3009120), MEK (trametinib), or AMPK (compound C). The combination was found to be specific for RAS/RAF–mutant cells and had no significant effect in RAS/RAF–wild-type keratinocytes or melanoma cells. In vivo treatment of human xenografts in NSG mice with sorafenib and aspirin significantly reduced tumor volume compared with each single-agent treatment. Conclusions: Combination sorafenib and aspirin exerts cytotoxicity against RAS/RAF–mutant cells by simultaneously affecting two independent pathways and represents a promising novel strategy for the treatment of RAS-mutant cancers. Clin Cancer Res 24(5) 1090–102. ©2017 AACR.

Meeting report from the 7th International Melanoma Congress, Sydney, November, 2010

Publisher: Wiley

Date: 22-12-2010

DOI: 10.1111/J.1755-148X.2010.00811.X

Targeting glutamine transport to suppress melanoma cell growth

Publisher: Wiley

Date: 17-02-2014

DOI: 10.1002/IJC.28749

Abstract: Amino acids, especially leucine and glutamine, are important for tumor cell growth, survival and metabolism. A range of different transporters deliver each specific amino acid into cells, some of which are increased in cancer. These amino acids consequently activate the mTORC1 pathway and drive cell cycle progression. The leucine transporter LAT1/4F2hc heterodimer assembles as part of a large complex with the glutamine transporter ASCT2 to transport amino acids. In this study, we show that the expression of LAT1 and ASCT2 is significantly increased in human melanoma s les and is present in both BRAF(WT) (C8161 and WM852) and BRAF(V600E) mutant (1205Lu and 451Lu) melanoma cell lines. While inhibition of LAT1 by BCH did not suppress melanoma cell growth, the ASCT2 inhibitor BenSer significantly reduced both leucine and glutamine transport in melanoma cells, leading to inhibition of mTORC1 signaling. Cell proliferation and cell cycle progression were significantly reduced in the presence of BenSer in melanoma cells in 2D and 3D cell culture. This included reduced expression of the cell cycle regulators CDK1 and UBE2C. The importance of ASCT2 expression in melanoma was confirmed by shRNA knockdown, which inhibited glutamine uptake, mTORC1 signaling and cell proliferation. Taken together, our study demonstrates that ASCT2-mediated glutamine transport is a potential therapeutic target for both BRAF(WT) and BRAF(V600E) melanoma.

A stochastic mathematical model of 4D tumour spheroids with real-time fluorescent cell cycle labelling

Publisher: Cold Spring Harbor Laboratory

Date: 29-11-2021

DOI: 10.1101/2021.11.28.470300

Abstract: In vitro tumour spheroid experiments have been used to study avascular tumour growth and drug design for the last 50 years. Unlike simpler two-dimensional cell cultures, tumour spheroids exhibit heterogeneity within the growing population of cells that is thought to be related to spatial and temporal differences in nutrient availability. The recent development of real-time fluorescent cell cycle imaging allows us to identify the position and cell cycle status of in idual cells within the growing population, giving rise to the notion of a four-dimensional (4D) tumour spheroid. In this work we develop the first stochastic in idual-based model (IBM) of a 4D tumour spheroid and show that IBM simulation data qualitatively and quantitatively compare very well with experimental data from a suite of 4D tumour spheroid experiments performed with a primary human melanoma cell line. The IBM provides quantitative information about nutrient availability within the spheroid, which is important because it is very difficult to measure these data in standard tumour spheroid experiments. Software required to implement the IBM is available on GitHub, github.com/ProfMJSimpson/4DFUCCI .

Combined use of subclinical hydroxyurea and CHK1 inhibitor effectively controls melanoma and lung cancer progression, with reduced normal tissue toxicity compared to gemcitabine

Publisher: Wiley

Date: 14-06-2019

DOI: 10.1002/1878-0261.12497

Abstract: Drugs such as gemcitabine that increase replication stress are effective chemotherapeutics in a range of cancer settings. These drugs effectively block replication and promote DNA damage, triggering a cell cycle checkpoint response through the ATR–CHK1 pathway. Inhibiting this signalling pathway sensitises cells to killing by replication stress‐inducing drugs. Here, we investigated the effect of low‐level replication stress induced by low concentrations ( 0.2 m m ) of the reversible ribonucleotide reductase inhibitor hydroxyurea (HU), which slows S‐phase progression but has little effect on cell viability or proliferation. We demonstrate that HU effectively synergises with CHK1, but not ATR inhibition, in 70% of melanoma and non‐small‐cell lung cancer cells assessed, resulting in apoptosis and complete loss of proliferative potential in vitro and in vivo . Normal fibroblasts and haemopoietic cells retain viability and proliferative potential following exposure to CHK1 inhibitor plus low doses of HU, but normal cells exposed to CHK1 inhibitor combined with submicromolar concentrations of gemcitabine exhibited complete loss of proliferative potential. The effects of gemcitabine on normal tissue correlate with irreversible ATR–CHK1 pathway activation, whereas low doses of HU reversibly activate CHK1 independently of ATR. The combined use of CHK1 inhibitor and subclinical HU also triggered an inflammatory response involving the recruitment of macrophages in vivo . These data indicate that combining CHK1 inhibitor with subclinical HU is superior to combination with gemcitabine, as it provides equal anticancer efficacy but with reduced normal tissue toxicity. These data suggest a significant proportion of melanoma and lung cancer patients could benefit from treatment with this drug combination.

Endogenous Replication Stress Marks Melanomas Sensitive to CHEK1 Inhibitors In Vivo

Publisher: American Association for Cancer Research (AACR)

Date: 14-06-2018

DOI: 10.1158/1078-0432.CCR-17-2701

Abstract: Purpose: Checkpoint kinase 1 inhibitors (CHEK1i) have single-agent activity in vitro and in vivo. Here, we have investigated the molecular basis of this activity. Experimental Design: We have assessed a panel of melanoma cell lines for their sensitivity to the CHEK1i GNE-323 and GDC-0575 in vitro and in vivo. The effects of these compounds on responses to DNA replication stress were analyzed in the hypersensitive cell lines. Results: A subset of melanoma cell lines is hypersensitive to CHEK1i-induced cell death in vitro, and the drug effectively inhibits tumor growth in vivo. In the hypersensitive cell lines, GNE-323 triggers cell death without cells entering mitosis. CHEK1i treatment triggers strong RPA2 hyperphosphorylation and increased DNA damage in only hypersensitive cells. The increased replication stress was associated with a defective S-phase cell-cycle checkpoint. The number and intensity of pRPA2 Ser4/8 foci in untreated tumors appeared to be a marker of elevated replication stress correlated with sensitivity to CHEK1i. Conclusions: CHEK1i have single-agent activity in a subset of melanomas with elevated endogenous replication stress. CHEK1i treatment strongly increased this replication stress and DNA damage, and this correlated with increased cell death. The level of endogenous replication is marked by the pRPA2Ser4/8 foci in the untreated tumors, and may be a useful marker of replication stress in vivo. Clin Cancer Res 24(12) 2901–12. ©2018 AACR.

University Of Queensland

Location: Australia

View Organisation

Discovery Projects - Grant ID: DP1096674

Start Date: 02-2010

End Date: 02-2013

Amount: $480,000.00

Funder: Australian Research Council

Discovery Projects - Grant ID: DP200100177

Start Date: 06-2020

End Date: 12-2024

Amount: $495,000.00

Funder: Australian Research Council